Dr. Jeff Hersh: What's in your picnic basket?

More than 76 million cases of food-borne illnesses occur per year in the U.S., affecting about a quarter of our population.

Dr. Jeff Hersh

Q: Several of us got sick after our family picnic and we are pretty sure it was something we ate. How common is food poisoning?

A: There are more than 250 different food-borne diseases, and illness from them is very common. Diarrhea, most often caused by food-borne or waterborne diseases, is a leading cause of death throughout the world. About 1 in 5 childhood deaths in developing countries is from diarrhea.

More than 76 million cases of food-borne illnesses occur per year in the U.S., affecting about a quarter of our population. Although most of these illnesses are self-limited (requiring only fluids by mouth to prevent dehydration), some are severe; more than 300,000 people (1 in 100 Americans) require hospitalization for food-borne illnesses, and more than 5,000 die.

Food-borne illness occurs in two ways, ingestion of a toxin or ingestion of an infectious agent.

- Parasites: in the U.S., the only common ones are giardia (also called beaver fever, it can also infect certain animals and is contracted from contaminated water) and cryptosporidium, but worldwide there are many others.

- Prions: such as the agent in mad cow disease

Toxins are sometimes found in seafood (for example, ciguatera or scrombroid), mushrooms, on produce (pesticides) or in many other foods. Toxins are also produced by infectious agents; for example, staph aureus toxin can sometimes be found in mayonnaise that sits out too long, and botulinum toxin can sometimes be found in improperly processed home-canned foods.

The specific symptoms from food-borne illnesses depend on the causative agent, but commonly include gastrointestinal symptoms such as abdominal pain/cramps, nausea/vomiting, diarrhea (which can be bloody from certain illnesses), as well as nonspecific symptoms such as fever, weakness, headache and malaise.

Treatment is based on the clinical picture; more than 80 percent of food-borne illnesses do not have a causative agent identified. Supportive care with symptomatic treatment and aggressive oral fluids (avoiding solid foods until symptoms improve and avoiding dairy products since some gastrointestinal illnesses cause transient lactose intolerance) is usually all that is needed. People with mild symptoms usually get better within a few days.

However, people who develop severe symptoms and cannot keep fluids down, have bloody diarrhea, high fever, severe abdominal pain or complications (such as lightheadedness from dehydration or symptoms suggestive of other organ involvement) should seek medical care.

There are many things that can be done to help minimize the chances of getting a food-borne illness:

- Buy your food from a trustworthy source.

- Wash all produce thoroughly before eating it.

- Keep kitchen surfaces clean, especially after preparing raw meat.

- Refrigerate foods that require it.

- Thaw frozen foods properly (in the refrigerator or using a microwave).

- Cook foods thoroughly; for example, use a thermometer to ensure meat is cooked thoroughly.

- Clean your hands after preparing food and before eating.

The Centers for Disease Control and Prevention have a surveillance program, FoodNet Surveillance, to identify outbreaks of food-borne illness. In fact, just last week there was a recall of alfalfa sprouts after 23 people became ill from salmonella.

The good news is that many food-borne illnesses are occurring less frequently than 10 years ago. For example, the incidence of shiga toxin Escherichia coli is down 41 percent, salmonella is down 10 percent, listeria is down 26 percent, campylobacter is down 30 percent, Yesinia is down 53 percent and shigella is down 55 percent. Vibrio is the exception and is up 85 percent.

There is yet another reason for close surveillance of food-borne disease -- to be vigilant against terrorist attacks. In 1984, a domestic cult (Rajneeshee) put salmonella in a restaurant salad that made more than 750 people ill.

Follow the guidance above to help minimize your chances of acquiring a food-borne illness, but if you think you have developed one, report it to your local health department. The earlier an outbreak of food-borne illness is identified, the sooner it can be contained and the less people affected.